Robert Wayne Gladden, Jr., was also charged with first-degree assault and was being held without bail at the Baltimore County Detention Center, Baltimore County police said early Tuesday. The Associated Press is not identifying the teen or his family because he is a juvenile. Police plan to hold a news conference later Tuesday.
Meanwhile, about 150 students turned out for a prayer vigil organized by local churches on the grounds of the school.
Authorities say the student opened fire Monday at Perry Hall High School, allegedly getting off two shots and wounding a classmate before being rushed by teachers. The 17-year-old victim remained in critical condition at Maryland Shock Trauma Center on Monday evening, a hospital spokeswoman said.
The suspect's father spoke to a reporter at his home that evening and said his son was the shooter. When asked about a motive for the shooting, the father indicated his son had been bullied. He gave no further details.
A woman who was also at the home and said she was related to the father, gave the following statement on the family's behalf: "We are horrified. We did not see this coming and our thoughts and prayers are with the victim and the victim's family."