Police say they still don't know why an enraged driver raced into an Aurora church parking lot Sunday, crashed his car and then wordlessly opened fire on church members who were rushing to help him.The gunman, Kiarron Parker, 29, of Denver, shot and killed 67-year-old Josephine Echols, the mother of De Lono Straham, the pastor of The Destiny Christian Center, Aurora police spokesman Frank Fania said at a Tuesday afternoon news conference.Echols' nephew, an off-duty Denver police officer who was attending a church service, pulled his gun and exchanged gunfire with Parker, Fania said.Denver police identified the off-duty officer as Antonio Milow, a six-year veteran.While it is assumed that Milow shot and killed the gunman, Fania would not confirm that, saying it is part of an ongoing officer-involved-shooting investigation.Yet, Fania agreed the Milow likely prevented more bloodshed."Who knows what would have happened had that officer not been there or had his gun with him," the police spokesman said. "It certainly had the makings to be a lot worse."Parker and Echols died from multiple gunshot wounds, the Arapahoe County Coroner's Office said Tuesday.Police are still puzzled about why Parker, who had a long history of convictions for drug possession, illegal weapon possession and resisting arrest, opened fire on people leaving the church just before 3 p.m. Sunday."We don't know why the gunman did this," Fania said. "We believe that there was no connection with the gunman to this church."Fania said investigators are hoping that toxicology tests, which detect drug and alcohol use, may "shed some light on why he acted the way he did."Just before the shooting, a male friend said Parker had become upset on nearby Dartmouth Avenue, Fania said."We're not sure why he became upset," Fania said.Parker jumped in his gray Dodge Charger and tore off, the friend told police. The friend, worried about Parker and what he might do, tried to drive after Parker but lost him, Fania said.Witnesses said Parker came tearing around a corner into the church parking lot, leaving curving tire burns before he crashed into a car.As churchgoers ran up to check on the man, Parker pointed a handgun at a man from the church and pulled the trigger, but the gun jammed, Fania said.While Parker tried to clear the jam, the churchgoer was able to escape.Unfortunately, Echols, a longtime nurse, arrived just as the Parker fixed the gun and he repeatedly shot her, Fania said."All the witnesses we've talked to said the gunman made no comments whatsoever" as he fired, Fania said.Meanwhile, Straham, the pastor, said he hurried to protect people inside the church,"Once I heard the gunshots, I got everybody hidden into two separate rooms," Straham told 7NEWS. "I kind of looked back and saw the gunman just firing."Children screamed as Straham ushered them to cover."It was just difficult seeing the looks on their faces when the gunshots went off. It was horrible," he said.Straham said his cousin, Milow, "took the door once we secured everyone and began to exchange fire with (the gunman).""It was very fortunate because (Milow) normally doesnt even carry his revolver," Straham said. "I believe my cousin saved a lot of peoples lives that day."Straham said he heard a scream and thinks it was his mother perhaps trying to distract the shooter."Im not sure if she yelled to distract him or not, or if she just couldnt get away," Straham said.Straham said his mother had run out to see if she could help the victim of the car crash.Milow shot the gunman, the pastor said.Straham said he was "devastated" to see his dying mother on the ground."I saw my mom stretched out, and I ran and checked on her, and she had a bullet hole in her face, and she was bleeding all over," Straham said."Im saddened. My heart is hurt," Straham said. "Im devastated that my mom lost her life actually trying to help someone that took her life."Parker has an eight-page Colorado criminal history, including arrests for cocaine dealing, illegal weapon possession, resisting arrest and repeatedly driving with a suspended license.His state arrest report said he went by the street nickname "Little Snoop" or "Lil' Snoop," and his body was covered with tattoos.Aurora police have no indications that Parker was a gang member, Fania said.In 2001, Parker was arrested in Aurora and charged with possession of cocaine for sale, according to court records. He pleaded guilty to felony drug possession in 2002 and was sentenced to three years in state prison and given credit for 19 months served.Later in 2002, Parker pleaded guilty to illegal weapon possession, records state.Parker was released from prison, but his parole was revoked in 2005 and he was sent back to prison for a five-year term, court records state.