ABC News' Dan Harris and Natasha Singh report:

A Connecticut shelter dog is being credited with saving the life of an infant who had stopped breathing.

The dog, named Duke, alerted the baby's parents that something was amiss by jumping into their bed in the middle of the night. The dog was shaking uncontrollably.

"He's insanely obedient so this was extremely bizarre," Jenna Brousseau, speaking in an interview with WFSB-TV, said of Duke's Oct. 7 behavior.

She and her husband decided to check on their daughter, 9-week-old Harper. They found that she wasn't breathing.

"My husband called 911 and the ambulance came here and it was because of our Dukie dog, who alerted us," Brousseau of Portland, Conn., said, according to WFSB-TV. "If Duke hadn't, you know, been so scared, then we would have just gone to sleep."

Doctors aren't sure what caused Harper to stop breathing, but have said it could possibly have been because of acid reflux.

The Brousseaus adopted Duke from a shelter six years ago.

"He's the perfect dog," Brousseau said. "He was meant to be ours, and meant to be hers."

Harper is apparently doing well now.