The brazen incident occurred around 3 p.m. at the branch located on the 13600 block of Van Nuys Boulevard.
Police say the victims were confronted by the armed suspect as they attempted to walk into the library. The suspect then forced the two into their 2004 Toyota Tundra.
That's when the father was forced to drive to a Citibank ATM machine in Van Nuys and withdraw $900. The suspect then dropped the two victims off on the interchange that binds the 5 and 14 freeways, and took off in their truck. A California Highway Patrol officer shortly picked the victims up.
The truck was equipped with LoJack, and police have since located the vehicle near Adelphia Avenue and Lazard Street in Sylmar.
No injuries were reported.
A description of the suspect was not immediately available. The investigation remains ongoing.
Anyone with information on the incident was urged to contact police at LAPD-24-7.