Jim O'Connor sometimes comes across as cold.
The calculus and algebra teacher at St. Francis High School near Los Angeles can be tough, his students told CBS Evening News.
But, last November, one of the teens found out that O'Connor is actually as sweet as they come.
While visiting Children's Hospital Los Angeles, the student discovered that the math teacher volunteers after school at the hospital -- and usually he can be found cuddling sick babies, CBS reported earlier this month.
O'Connor is also the hospital's top blood donor, according to the Los Angeles Times. He's donated more than 72 gallons of blood and platelets, the paper reported.
Indeed, in the video below, it's hard to imagine the math teacher as anything but kind, as he comforts infants when their parents aren't able to be there.
"I know [I'm not a tough guy]," he told CBS. "But don't tell my students."