A five-year-old boy fell three flights from a Loudoun County apartment Tuesday night, but a Loudoun Sheriff’s Deputy saved his four-year-old cousin from the same fate, authorities said.

Deputy Casey Johnson was responding to a call around 8:30 p.m. Tuesday from an apartment complex on Wallingford Square in Sterling. A five-year-old had reportedly fallen from a third-story balcony, according to authorities.

The boy was sent to Landsowne Campus of INOVA Loudoun Hospital with non-life-threatening injuries, authorities said.

The first emergency worker to the scene, Johnson said he arrived at the apartment, inspected the five-year-old already on the ground and surrounded by a crowd and looked up to see a girl crying and clutching the balcony railing. The girl had climbed over to try to save her cousin but couldn’t climb back, he said.

Johnson told her to hang on, ran up the stairs, knocked on the door for about 30 seconds, then tried to kick the door down when no one responded. Once he kicked at the door a second time, an adult female family member opened it, he told her what happened, rushed to the balcony and grabbed the child, he said.

“As soon as she held on to me and she knew she was safe, I felt very, very happy that I pulled her back and she was safe,” he said. “She finally started to smile a little.”

Johnson, who joined the Loudoun force in 2008, said the investigation of the incident has moved from his office to Child Protective Services.

“It is summer time and people have to keep an eye on their kids,” he added.