Gary Stokes of the 6700 block of Richardson Road in Gwynn Oak is being held without bail at the Baltimore County Detention Center on charges of attempted first-degree murder, assault and armed robbery.
Police said Blackmon is an employee at the Social Security Administration and was taking a stroll about 11:45 a.m. when he was attacked near the Walden Circle townhouse community, just south of the campus near Interstate 70.
Charging documents filed in court Tuesday say the victim flagged down a passing police officer near Woodlawn Drive and Parallel Road, and told him he had been robbed and shot.
Authorities said the attack occurred on a path that connects Parallel Road, which skirts Social Security Administration parking lots, and the townhouse development. Police said Blackmon had a single gunshot wound to his right biceps.
The victim gave police a description and said the gunman ran north. Shortly after, police arrested Stokes in the 1500 block of Woodlawn Drive, a quarter-mile from where Blackmon had collapsed.
Police charging documents said the suspect matched the description provided by the victim, who was treated at Sinai Hospital in Northwest Baltimore. The documents say Blackmon picked the suspect out of a photo lineup.
According to court records, Stokes pleaded guilty in August 2010 to attempted robbery with a deadly weapon and was sentenced to 10 years in prison, with all but nine months suspended. He was placed on two years probation.
Prosecutors dropped a charge of attempted first-degree murder in the case.
John Cox, a deputy state's attorney for Baltimore County, said attempted robbery with a deadly weapon was a more accurate charge. During the 2009 robbery attempt, he said, the victims grabbed at the robbers' weapons, which were fired during a struggle.
Baltimore Sun reporter Steve Kilar contributed to this article.