SAN MARCOS, TEXAS — Four months following a deadly fire at the Iconic Village Apartments in San Marcos, the Bureau of Alcohol. Tobacco, Firearms and Explosives has confirmed that the blaze was intentionally set, and they are offering reward money for information that is useful in the ongoing criminal investigation.

"We are 100 percent confident that this was intentionally set," ATF Special Agent in Charge Fred Milanowski said. He added that the ATF spent 10 days at the scene of the crime gathering evidence and information from witnesses to come to the conclusion that the fire wasn't an accident.

RELATED: Fatal San Marcos apartment fire being investigated as criminal act

The fire on July 20, 2018, killed four Texas State University students and another person.

ATF said at a news conference Friday, Nov. 30, that their main focus is on identifying the suspect or suspects, and they're offering a $10,000 reward for information that leads to an arrest. Milanowski said investigators are confident that there could be people out there that heard something before or after the fire happened that could be helpful in the ATF's investigation.

RELATED: Former Iconic Village Apartments residents want closure following fire

Milanowski said the ATF isn't releasing information on exactly when, where, or how the fire was set -- as that information is a part of the criminal investigation.

RAW: Fatal San Marcos apartment fire was intentional, ATF says

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The San Marcos Fire Marshal Kelly Kistner said they spoke with family members Friday about the updated classification for the cause of the fire. Fire Marshal Kelly Kistner said the death certificates for the victims are undetermined, pending the results of the investigation. Kistner said the San Marcos Fire Department will partner with the ATF, the local justice of the peace and medical examiner's office to re-evaluate the cause of death for the victims.

The investigation is ongoing. Anyone with information about the incident is asked to contact 1-888-ATF-TIPS.

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This latest news rattled former residents of the apartments -- like Tyler Brockington, who was roommate to Dru Estes, one of the five victims.

He was in Katy at the time of the fire.

"What if I had been there?" he said. "Could I have waken him up?"

He wants closure.

"Now that I know that it was somebody that did this," he said. "This was the will of an individual...I haven't been able, haven't had time to work through those kind of feelings."