A 51-year-old man pleaded guilty to robbing three elderly people, two at knifepoint, in Hyattsville in November 2011 during an outburst of crime that terrorized the community, according to the Prince George’s County state’s attorney’s office.

Henry Sanders of Hagerstown, Md., could receive up to 55 years in prison for each offense, according to prosecutors. A sentencing date has not been set. He pleaded guilty Friday.

Sanders faces similar charges in Montgomery County, where authorities have accused him of five violent attacks in 10 days, including four robberies in which he allegedly tried to abduct the victims to get their bank cards. He has not been tried in those cases.

In a statement, Prince George’s County State’s Attorney Angela Alsobrooks said she “is pleased that [Sanders] is being held accountable for his crimes. Protecting our most vulnerable populations is paramount to me, and our citizens can rest assured that Mr. Sanders will not be terrorizing our community any longer.”

The attacks to which Sanders pleaded guilty include one Nov. 18, 2011, in which the victim was a 79-year-old man who agreed to take Sanders to the hospital to visit his sick mother. In the car, authorities said, Sanders punched the man in the face and head, demanded his silver 2001 Toyota Solara and then took the man’s wallet and credit card, which he used at a Shell station in Beltsville.

On Nov. 20, authorities said, Sanders asked an elderly man in a Home Depot for a ride to a Metro station. As the man was driving, Sanders threatened him with a knife, took his wallet and ordered him to go to a bank to withdraw money at an ATM.

On Nov. 25, authorities said, he threatened a woman, also described as elderly, with a box cutter as she walked to her car and then took her purse.

In a Montgomery case, he allegedly forced a 77-year-old man to withdraw money from three ATM accounts and got away with $1,800. The victim was hit repeatedly in the face and suffered a cut leg and a broken nose, police said.