Raleigh, N.C. — Raleigh police said Monday they believe two additional robberies might be linked to seven area hold-ups, including one that ended in a homicide.

The two robberies happened on Feb. 1 and Feb. 13 at a Wilco-Hess convenience store at 7413 Louisburg Road at approximately 5 a.m. as the store clerk was opening for the day.

Most of the other robberies also occurred when the businesses – convenience stores and fast-food restaurants – were either opening or closing. Most of the clerks involved were female.

Police spokesman Jim Sughrue said Monday that although investigators do not know for certain whether the crimes are related, the assailant in each crime used a handgun and that his description was similar – a black man in his 20s to 30s, approximately 6 feet tall and with an athletic build.

In one robbery, on April 10, Stephanie Anderson, a clerk, was shot to death as she opened the Wilco-Hess at 1741 Trawick Road. Last month, a clerk at Mexico Lindo on Wake Forest Road was injured when she was shot.

Authorities say the person they believe is responsible for those crimes often surveys his targets and might enter the business, walk around and leave without buying anything.

Police consider him armed and dangerous and urge store employees to use "extreme caution" at opening and closing times. They urged businesses to have multiple employees working then. They also encourage employees to pay close attention to areas around their stores at those times.

Investigators are offering a reward for information that materially assists in the cases, and they have set up a 24-hour tip line at 919-227-6220 for the public to call. Crime Stoppers is also taking calls at 919-226-CRIME.

Wilco-Hess, which operates the convenience store where Anderson worked, has offered a $25,000 reward in the case.