Images of the shootout and siege, scenes that once gripped viewers around the globe but which long since have faded from the public consciousness, still streak through Aguilera's mind.
He was the ATF agent whose firearms investigation of the Branch Davidians led to a raid on their compound near Waco on Feb. 28, 1993.
The ill-fated raid claimed four U.S. Bureau of Alcohol, Tobacco and Firearms agents and six Davidians and sparked a 51-day standoff that ended in the deaths of 76 Davidians - including the religious sect's leader, David Koresh.
"These are scenes I relive every day, especially at that time of year," said Aguilera, 47. "Although I've been able to control it somewhat, it's something you never forget."
Memories of the tragedy have tormented Aguilera, causing emotional trauma, feelings of guilt and failed relationships, and in 1994 he left Texas for another job.
The move enabled him to further his career while escaping the past and the negative publicity surrounding Waco.
But now, in a new twist on an old story, Aguilera has returned. He's heading the ATF field office in San Antonio, the latest stop on a road that has taken him to agency jobs in Mexico and supervisory posts in New Jersey and Washington.
In coming home to Texas, the veteran federal agent who was shot at in Waco finds himself in another challenging confrontation: facing down his own past.
"It was something painful I had to go through in life," he said of Waco, "and I had to come back and face it, just accept it."
Aguilera hopes his homecoming will facilitate the healing process and help bring the Waco chapter of his life to a close.
"It's an experience you don't want to ever experience again," he said. "What could have been an easy resolution turned out be a tragedy."
What happened that day brought a firestorm of criticism.
"It was the biggest disaster in law enforcement history," said Dave Hardy of Tucson, Ariz., a lawyer involved in an unsuccessful wrongful death suit against the government over Waco.
"Foul-up is far too mild. In a situation where you have 10 possible decisions, they consistently picked the worst. It's just, 'My God, what were they thinking?'"
Critics took the ATF to task for the way it handled the initial raid and questioned Aguilera's investigation. They blasted the FBI for its handling of the ensuing siege.
Civil lawsuits, congressional probes and a federal prosecutor's report that dismissed many allegations stemming from the Waco raid did little to quietthe clamoring for justice.
Michael White, president of the American Civil Liberties Union of San Antonio, said a cloud remains over the agents involved.
"I don't know how much responsibility (Aguilera) had, but the way it was carried out was a fiasco," White said of Waco. "It didn't have to go that way."
Aguilera's memories of the raid are vivid. But citing the possibility of further litigation by relatives of some Branch Davidians, he said he "can only reflect on my feelings and what I observed and what's already been made public."
On the morning of the raid, Aguilera and other agents went to the Mount Carmel compound to arrest Koresh and serve a search warrant alleging that Koresh and his followers were stockpiling illegal automatic weapons and explosives.
Aguilera boarded one of three helicopters - what he said was part of an airborne diversion - while agents rode cattle trailers and headed for the compound's doors.
Versions from critics and the government differ on the encounter, disagreeing even on who fired first.
Aguilera said bullets from the Davidians struck the helicopter he was in, forcing it to make an emergency landing.
Critics charged that ATF agents shot from the choppers at the Davidians first, and that the FBI knocked down the walls with tanks in the subsequent siege to hide evidence proving that theory.
In his measured account of what happened, Aguilera said the investigation was warranted and that the numerous illegal firearms and rounds of ammunition found show the probe was on target.
"We didn't do anything wrong," Aguilera said. "The media just made it look like we were the bad guys, when in fact we were doing what warranted the execution of that warrant."
But Aguilera acknowledged he has struggled with his feelings over the results.
"Initially, I felt guilty because I had opened up this investigation. I thought, 'If I had not opened this, people would have not gotten killed or wounded or hurt by this,'" Aguilera said. "I have come to understand now that this had to be done because who knows what these people had in store for the local community down the road, or in the future."
ATF agent Roland Ballesteros, whose thumb was partly shot off after he approached the compound's doors and spoke briefly to Koresh, said Aguilera made the right calls in his part of the investigation.
"He wanted to step aside and take a look to see if it could have been handled differently," Ballesteros said. "To be honest with you, I don't think it could have. He did the job that he was supposed to do, and he did a good job."
Aguilera, who assumed his current post in July, is the first Hispanic to hold the ATF title of resident agent in charge in San Antonio, part of the agency's Houston division.
The son of immigrant parents, Aguilera said his father, who labored in steel mills in Indiana and later became a contractor in Joliet, Ill., called for his 10 children to better themselves. Aguilera was the middle sibling of seven boys and three sisters.
"He would take us to work. The intent was to stress the importance of an education," Aguilera said of his father. "He would say, 'It's either this or something better.' I was the first one out of there."
Aguilera joined the Marines to help pay for college, earning a bachelor's in history at the University of Illinois while working as a police officer in his native city. Stints followed later with the Border Patrol in South Texas and the ATF.
He said his training and experience helped him "keep my head above water" and move forward, even when bumps emerged.
Aguilera is unmarried, though he has two daughters - April, 22, and Miechaela, 12 - who live elsewhere but with whom he has frequent contact.
"It's just been really difficult to establish a relationship," Aguilera said of his reasons for being single.
He attributes that to his passion for the job, and frequent moves. He also acknowledges Waco had a hand in his lifestyle.
"I was seeing somebody at the time, but this was so much pressure, it was such a significant emotional event, that (the relationship) didn't materialize," he said.
Now the head of a 10-agent office, Aguilera enthusiastically talks about his plans to make the ATF more recognizable for its assault on crime rather than how it's seen in some circles - synonymous with Waco.
He said he plans to increasingly push federal initiatives like the Safe Streets program, which attempts to keep guns out of the hands of felons, and the Youth Crime Gun Interdiction Initiative, a collaboration with state and local law officers that aims to disrupt the flow of firearms to juveniles.
He said he plans to be more involved with local and state agencies in the 20-plus counties surrounding San Antonio that his office covers. Furthermore, he wants to reach out to the community, partly by pitching the agency to college students as a career choice.
"I'm hoping to help reduce crime and take some guns off the streets," Aguilera said. "I'm coming here to make a positive impact on the community."
Ballesteros, who has known Aguilera since their days at the ATF training academy in 1987, sees Aguilera's perseverance and determination as a breath of fresh air for others who might want to abandon their professions during difficult times.
"I was afraid that all of the fallout from (Waco) would have changed his attitudes about his career," Ballesteros said. "He'll tackle that role, as a resident agent, as he did as a street agent, basically just immerse himself into it and do the best job anybody can possibly do and run a course until justice is done. That's the kind of guy he is, and I respect him for it."
Aguilera thinks putting Waco behind him will take time. Talking to Ballesteros and other agents who were part of the investigation - looking to them for support - is part of the healing process.
"It's been 10 years and really, I've just begun to heal," Aguilera said.
"Life has to go on. I have to put this behind me and I have to go forward."