By Eliott C. McLaughlin and Darran Simon

CNN

(CNN) -- The gunman who shot and injured a paramedic treating a civilian in Dallas claimed on his Facebook page to be the New Black Panther Party's longtime national minister of defense.

Derick Lamont Brown was later found dead from a "self-inflicted wound" when a police robot searched a home on the block where the shooting occurred, Mayor Mike Rawlings said.

A second deceased person was found in the same home. Police have not identified the second person other than to say the person was a Dallas resident.

The paramedic and his patient remained in intensive care as of late Monday.

The incident began as a "simple dispute between two neighbors that escalated into a shooting," interim Chief David Pughes of the Dallas Police Department said.

The paramedics apparently believed they were responding to a suicide call, Dallas Fire-Rescue Department Chief David Coatney told reporters.

"They served to try to take care of a citizen," the chief said. "Unfortunately, we had a tragic event where they were shot at."

Criminal history

Brown had numerous charges on his record, mostly involving drugs, weapons or driving while intoxicated, as well as several misdemeanors, and in most of the cases he took plea agreements, court records show.

He was sentenced to jail on at least nine occasions, but it was not clear from inmate records how much time he'd actually served, court documents show.

Brown went by "Brotha Dk" on Facebook, where he posted occasionally about the New Black Panthers and on at least one occasion in 2014 shared a photo of himself holding a single-barrel shotgun. He had served as the organization's defense minister since 1998, according to the Facebook page.

A law enforcement source familiar with the investigation confirmed the page belonged to Brown.

The New Black Panther Party did not respond to CNN's email seeking comment on Brown's relationship to the organization.

Southern Poverty Law Center describes the New Black Panthers as a black separatist group known for "its anti-white and anti-Semitic hatred."

The new group has no affiliation with the original left-wing militant group of the 1960s and 1970s, the SPLC says. That echoes a 2014 statement issued by the Dr. Huey P. Newton Foundation, named for the original Black Panther Party's co-founder, which read, "The people in the New Black Panthers were never members of the Black Panther Party and have no legitimate claim on the Party's name."

'Above and beyond'

Dallas police officers responded to an active shooter call around 11:30 a.m. Monday and arrived to discover an ambulance at the scene. The officers also found the paramedic and another person down in the street, Pughes said.

It is believed the gunman was in the street shooting at that point, Pughes said. Officers took cover from the gunfire, he said.

Then a police sergeant arrived and noticed the paramedic was severely wounded, Pughes said. The unidentified officer "went above and beyond, as many of the Dallas police officers do each and every day," he said.

"He went in alone, and he pulled the paramedic out, placed him in his squad car and drove him to Baylor Hospital," Pughes said.

Dallas officials credited the officer with saving the paramedic's life.

"In my mind, someone that was not mentally stable dealt a lot of pain this afternoon," Rawlings said. "And our heroic paramedic stepped in to help a citizen putting their lives on the line."

The officer "rescued that individual, and now the doctors get to do their part," the mayor said.

"That's how we come together as a city to protect each other, to have each other's back," Rawlings said.

Paramedic, citizen now recovering

The injured paramedic underwent surgery Monday afternoon and was in critical but stable condition," Rawlings said. The paramedic and the wounded citizen were in the intensive care unit at a local hospital.

Another Dallas officer was also treated at the scene for an unspecified injury, authorities said.

Police closed roads near the intersection of Interstate 30 and Dolphin Street shortly after the shooting.

"Confirming 1 paramedic shot while responding to a call. No detail at this time. Thoughts and prayers are with all impacted," Dallas Fire-Rescue tweeted at that time.

The shooting happened near the Dallas Fire-Rescue's Dodd J. Miller Training Center, about a quarter-mile south of Interstate 30.

The FBI is assisting Dallas police in the investigation, according to FBI spokeswoman Lauren Hagee.

CNN's Ed Lavandera, AnneClarie Stapleton, MaryLynn Ryan, Tina Burnside and Dave Alsup contributed to this report.