Derick Lamont Brown was acting erratically at his home before he forced his 67-year-old roommate into a back room and fatally shot him Monday, said Randy Blankenbaker, Dallas' assistant police chief of investigations. The gunshots prompted a neighbor to go outside, where Brown shot him.

DALLAS A 36-year-old man with a criminal history killed his roommate, shot his neighbor and opened fire on responding paramedics in a Dallas neighborhood during an attack that prompted police to barricade the area for hours, investigators said Tuesday.

Derick Lamont Brown was acting erratically at his home before he forced his 67-year-old roommate into a back room and fatally shot him Monday, said Randy Blankenbaker, Dallas' assistant police chief of investigations. The gunshots prompted a neighbor to go outside, where Brown shot him.

Armed with a semi-automatic rifle, Brown then fired at emergency responders trying to help his neighbor, critically wounding a paramedic, Blankenbaker said. Brown also fired at police officers, including one officer who sustained an injury to his calf, possibly from gunfire, the assistant chief said.

Officers exposed themselves to gunfire as they carried the injured paramedic into a squad car and rushed him to a hospital, the commander said. When Brown pointed his rifle at an approaching officer, another officer shot and injured Brown, who then retreated into his home, Blankenbaker said.

"All of these officers' actions are more than commendable. They should be considered heroic," Blankenbaker said during a news conference.

The paramedic, William An, and the neighbor, whose name hasn't been released, were rushed to the hospital in critical condition. The shooting was initially reported as a possible suicide, which added to the confusion as officers arrived, Blankenbaker said.

The attack prompted police to block access to the area until a police robot searched Brown's home. The robot found Brown and his roommate dead. Police believe Brown died of a self-inflicted gunshot wound.

The paramedic underwent surgery Monday and was in critical but stable condition Tuesday at Baylor University Medical Center, Dallas Fire-Rescue spokesman Jason Evans said. Details about his injuries weren't released, though Dallas Mayor Mike Rawlings said Monday that the paramedic "is going to have to undergo extensive medical treatment to get him back up to par."

Evans said An is a 10-year veteran of Dallas Fire-Rescue and a married father of a 3-year-old child, with another child on the way.

Police didn't provide an update on the neighbor's condition Tuesday.

Blankenbaker said Brown's criminal history includes charges of aggravated assault, driving while intoxicated and illegal gun possession. Police said Brown was well-known by local, state and federal law enforcement because of his criminal history.

Brown also was a past leader of the New Black Panther Party in Dallas. He told The Dallas Morning News in 2004 that he wanted to empower people to stand up to the police, but that he wanted to stay away from the militant stereotype of the Black Panthers.

An FBI spokesman said the agency also was investigating Brown but declined to offer specifics.

Dozens of police vehicles swarmed the mostly residential area after the shooting was reported near a local Fire Training Academy. FBI agents and other federal officers also were in unmarked vehicles waiting at intersections in the neighborhood.

Several people from a nearby neighborhood and some relatives of people who live in the barricaded area gathered at a nearby gas station to await updates from police. Among them was 33-year-old Brenda Salazar, who told The Associated Press that her mother lived in the neighborhood and saw SWAT teams arrive Monday.

Salazar said she was headed to the area to visit her mother when she heard about the shooting on the radio. She called her mother, who told her she didn't hear any shooting but "saw the SWAT guys and police setting up and going into the neighborhood."

Salazar said her mother was OK and was watching the news, "but this stuff happens here all the time."

Texas Gov. Greg Abbott released a statement saying his prayers were going out to all those affected.