ROCKFORD — It took Jonny Castro 10 hours to create a digital portrait of Jacob Keltner, about the same time it took him to create portraits of the other 23 police officers killed in the line of duty so far this year in the U.S.

Keltner, a McHenry County sheriff's deputy working as a member of the U.S. Marshals Great Lakes Regional Task Force, was shot to death Thursday while trying to serve warrants for a Springfield man at a Rockford hotel.

Castro is a forensic artist with the Philadelphia Police Department who creates sketches of suspects and handles other art-related work for the department. He has digitally painted 450 portraits in the past three years. Most were fallen officers, and some were K-9s, firefighters, soldiers and crime victims. He does so on his own dime and on his own time.

His aim is to create portraits this year of every police officer killed on the job, he said in a telephone interview Monday. Castro often checks the Officer Down Memorial Page for the latest deaths. He uses a photo of the subject for guidance and paints the portrait in Photoshop, using a stylus.

Castro, 36, sent the Rockford Police Department a portrait of Jaimie Cox, who died Nov. 5, 2017, after becoming entangled with a vehicle driven by a man he'd stopped for a traffic violation. The department gave the portrait to Cox's widow, Caitlin. Andrea Cox, Jaimie's cousin, said Castro also gave Caitlin Cox a large wall portrait that she keeps in her home, and about 10 8-inch-by-10-inch images for her to give family and friends.

Sometimes, Castro mails a copy of his painting to the department of the departed officer to keep. "It's a way to give back to the departments and families," said Castro, who studied graphic design in college, spent four years in the Army, including a tour in Iraq, and worked as a patrol officer for nine years before taking the forensic graphic artist job three years ago.

On Wednesday, he will send 11-inch-by-14-inch prints of his Keltner portrait in shipping tubes to the McHenry County Sheriff's Department. "I did not want to bother the family," he said. Sometimes, if the subject is near Philadelphia, Castro, who is married and has children, will print the portrait on canvas, have it stretched, frame it and give it to a family member.

Families of fallen officers are quite appreciative. "The families usually contact me and will send pictures (of the portraits) hanging in their houses, or of children holding it in a frame," he said.