Derick Brown has been well known to the Dallas Police Department and federal authorities for years.

In 2004, he led protests against DPD and was previously the leader of the New Black Panther Party.

He and others members had confrontations with officers over police involved shootings.

He promised retaliation back then.

"And I mean if that takes fighting back. I mean Lord have mercy on me for about what is about to happen on these streets. But I am willing,” said Brown in 2004.

He has a long criminal history and the FBI confirmed they were currently investigating Brown.

"Mr. Brown's rap sheet, his encounters with law enforcement are well known at this time and they were known prior to this matter happening,” said FBI Special Agent in Charge Eric Jackson.

But, it may not have been known to Dallas Fire Rescue as they came face-to-face with Brown, Monday morning.

Police say he shot his elderly roommate Arthur Riggins. Then he shot his 24-year-old neighbor.

Brown’s girlfriend frantically called 911.

Firefighters arrived to find the neighbor shot in the middle of the street.

As they were helping him police say Brown shot firefighter William An who was taken by a DPD sergeant in his squad car to the hospital.

"All of these officers’ actions are more than commendable. They should be considered heroic,” said Asst. Chief Randy Blankenbaker.

Brown was found dead in his home.

Police say he shot himself. His family told WFAA he is a father of 18 and was expecting another child. He worked at Parkland hospital.

“We don't know what happened. We don't know what happened right now,” said Brandon Burton, Brown’s brother.

Dallas police say they are still trying to piece everything together and say a lot of what happened is captured on 911 recordings and surveillance tapes.