Booker was charged with armed robbery, general robbery, second-degree assault, conspiracy to commit robbery and theft in that robbery.
Booker had not been apprehended by Wednesday night.
Booker became a suspect as a result of tips provided by the public after information about the two robberies ran in The Herald-Mail, according to Lt. Rick Johnson.
Johnson said police don't know where Booker is staying. His last-known address is 424 N. Locust St. He is from Baltimore City but has friends in the Tri-State area, he said.
Earlier Wednesday, a man and a woman were charged in connection with the Dual Highway and Burhans Boulevard armed robberies.
Phillip Randolph Adams, 22, of 424 N. Locust St., was charged with one count each of armed robbery, general robbery, conspiracy to commit robbery and theft in connection with the two robberies.
Dana Marie Burcker, 21, of 116 N. Mulberry St., Apt. E, was charged with armed robbery, general robbery, conspiracy to commit robbery and theft in connection with the 7-Eleven armed robbery, city police said.
Adams was being held on $150,000 bond at the Washington County Detention Center. Burcker's bond was set at $50,000, jail officials said.
In the 7-Eleven armed robbery just before 10 p.m., a man entered the store, displayed a knife and demanded money from the cash register.
The clerk, Timothy E. Sorrell, was complying with the robber's demand when he was stabbed twice, police said.
Sorrell, 41, of Hagerstown, was discharged from Washington County Hospital on Tuesday, a hospital spokeswoman said.
After reports of the robberies appeared in the newspaper, witnesses notified police about a green Dodge Neon that was seen at both robberies, police said.
Booker was described as a black man, 6 feet, 2 inches tall, weighing 230 pounds, with black hair and brown eyes. He is 29 years old, police said.
Anyone with information about Booker's whereabouts can call police at 301-790-3700 Extension 234 or Crime Solvers of Washington County at 301-733-4141.
Staff writer Marlo Barnhart contributed to this story.