Updated at 8:15 p.m. Wednesday: Revised to include information about a possible accomplice.

Police are searching for an armed robber who killed a 27-year-old mother working at a Dollar General in Oak Cliff on Monday night, police say.

Gabrielle Simmons was behind the register at the store in the 4800 block of Sunnyvale Street when a man walked in about 7 p.m. and robbed her at gunpoint, police said.

After Simmons emptied the cash register, the robber shot her and ran west on 52nd Street, police said. He remains at large.

Surveillance footage shows one person possibly connected to the robbery running down the street. (Dallas Police Department)

Additional surveillance footage may point to the man having an accomplice who acted as a lookout, police said. A camera recorded two men running down a side street after the shooting,

Police Detective Scott Sayers told KDFW-TV (Channel 4) that Simmons managed to hit the alarm after she was shot, prompting the doors to shut automatically. The robber ran through the doors and dropped the till and bag he came with, leaving empty-handed, he said.

"I believe from the video that when he grabbed the till he had his finger on the trigger and the gun went off," Sayers said. "Now you know he still killed her and he's got to answer for that, but I want the individual to know that I understand that."

Anyone with information on the crime or the suspect can call police at 214-671-3647 or Crime Stoppers at 214-373-8477.

It's the third time that Dollar General location has been held up in the past year.

Mayor Pro Tem Dwaine Caraway said he spoke to Simmons after a previous robbery there, and she was scared for her safety.

"We now have six children from 7 months old up to 11 or 12 years old that will be without a parent," the council member said. "At the end of the day, it's about guns."

Speaking at City Hall, Caraway said the state and city have been hit particularly hard by gun violence — the July 7 ambush, the slaying of 13-year-old Shavon Randle over the summer and Sunday's massacre at a South Texas church — and suggested the National Rifle Association should find another locale for its convention next year.

"There's going to be a lot of people mad at me," said Caraway, a gun owner himself. "I don't care. We're going to have to start doing something."