Massachusetts Institute of Technology police officer Sean Collier was shot and killed by the Boston bombing suspects in 2013. This digital portrait of Collier is one of many created by Philadelphia police Officer Jonny Castro as a way of honoring first responders and military personnel for their sacrifices. Click through the gallery to see more of Castro's portraits.
Courtesy Jonny Castro
San Antonio Officer Miguel Moreno was shot and killed last June in Texas while investigating a vehicle break-in.
Courtesy Jonny Castro
Delaware State Police Cpl. Stephen Ballard was shot to death last April after stopping a suspect at a convenience store.
Courtesy Jonny Castro
North Carolina Department of Public Safety corrections Sgt. Meggan Callahan was beaten to death by a prison inmate last April.
Courtesy Jonny Castro
Lt. Debra Clayton of the Orlando Police Department was shot and killed last January in Florida after attempting to stop a murder suspect.
Courtesy Jonny Castro
Staff Sgt. James D. McNaughton of the US Army, 306th Military Police Battalion was shot and killed by an enemy sniper in Iraq in 2005.
Courtesy Jonny Castro
New Orleans Officer Marcus McNeil was fatally shot last October while on patrol.
Courtesy Jonny Castro
Florida Highway Patrol Master Sgt. William Bishop was hit by a vehicle while investigating a traffic accident last June.
Courtesy Jonny Castro
K-9 police dog Roscoe of Crowley, Louisiana, police was shot and killed while attempting to assist in the arrest of a murder suspect last March.
Courtesy Jonny Castro
Police Constable Keith Palmer of the Metropolitan Police Service was stabbed to death while defending London's Palace of Westminster during a terrorist attack last March.
Courtesy Jonny Castro
New York City Fire Department Chaplain Mychal Judge was killed in the September 11 terror attacks.
