The nonprofit group Mothers Against Murder is offering a $20,000 reward for information that leads to the arrest of the man who at gunpoint robbed a Taco Bell in south Palo Alto last month.

Palo Alto police announced on Friday that the nonprofit group offered the money to help obtain information about the Dec. 20 incident, which occurred just as the eatery at 910 East Charleston Road was closing. Police said an employee was in the store at about 12:30 a.m., preparing to close up for the night, when a man walked in with a handgun and demanded money from registers.

When the employee, a man in his 20s, gave him the money, the man demanded additional sums from the store, police said. The employee said he would go get more money from the back of the store but then used the back door to exit the Taco Bell, according to a police news release. He then watched the man leave the restaurant and drive off in a dark sedan along San Antonio Road toward U.S. Highway 101.

The employee said the man appeared to be in his late teens or early 20s, according to the news release. He was either white or Hispanic, and he was wearing a ski mask. There are no surveillance images available for release, and detectives have not developed any suspect information, according to the police.

Anyone with information is asked to call the department’s 24-hour dispatch center at 650-329-2413 or send anonymous tips to paloalto@tipnow.org or 650-383-8984.