One man is in custody after an attack with a crossbow left a man dead Thursday in the city's east end.

"The homicide squad has been notified," Const. Tony Vella, a Toronto Police spokesperson, told CTV Toronto.

The afternoon attack occurred inside the Main Street library, which is just south of Gerrard Street East, reported CTV Toronto's Naomi Parness.

When police arrived at 137 Main St., they located a male victim, estimated to be anywhere from his 30s to his 40s, with an arrow in his back.

Paramedics pronounced the victim dead at the scene.

Linus Smith said that as she sat in a restaurant across the street, she watched a man leave the library with something in his hand, get into a U-Haul van and drive off.

"He came out of the library, he was calm, he went into the U-Haul and he drove off," she said. "He didn't speed off or anything, he just drove."

Curious, she went to the library. A staff member told her a man got "hit" in the library, she said.

Another man came out of the library and took down the van's licence plate number, which was then passed to police.

Images from CTV Toronto's news helicopter showed police cruisers clustered away from the original crime scene. Others show a man sitting in the rear of a police cruiser.

Vella said an arrest was made in Scarborough. The suspect is believed to be in his 30s, he said.

The arrest location was near Phenix Drive and Hollis Avenue, which is southeast of Danforth Avenue and Birchmount Road. That location is about three kilometres east of the crime scene.

With a report from CTV Toronto's Naomi Parness and files from The Canadian Press