SPOKANE, Wash. -

Spokane Police arrested two people accused of robbing a McDonald's last night with an eight-month-old baby in their back seat and detectives think the pair are responsible for several other recent holdups.

This week there has been several robberies at fast food drive thrus where the suspect approaches the window on foot while another customer is in the middle of a transaction, grabs some cash from the drive thru and then bolts on foot.

Thursday night, as other customers waited in line for their dinner at McDonald's near the intersection of Belt and Wellesely in northwest Spokane, a masked man ran up to the drive thru, forced way inside the window and grabbed the drawer from the cashier.

What the thief didn't realize is that several witnesses would tail the suspect to his waiting get away car.

"I have to extend a word of gratitude to these people who are sitting there and are composed enough to see what is happening and take a moment to get a very, very good description," Spokane Police Captain Brad Arleth said.

Witnesses gave police a license plate that was traced back to a couple who had left their adult grandson in charge of watching their home on vacation.

Spokane Police that individual, 32-year-old Thomas Craigen, was using his grandfather's pickup for the drive thru hold ups.

"In this case, the witness information for the suspect vehicle did match that and it did provide us a license plate and that allowed us to hone in on the exact vehicle," Arleth said.

When patrol officers pulled over Craigen's vehicle they found 23-year-old Jessica Schwartzerburger behind the wheel and an eight-month-old baby in the back seat.

"We were able to apprehend these people with in an hour and the female suspect did have the child in the car so at this point the facts indicate that the baby was in the car during the robbery," Arleth said.

Both Craigen and Schwartzenburger have admitted guilt in Thursday night's robbery and admit they've been just trying to feed their drug habit.

Police are still looking for a third suspect in this case, the couple's drug dealer. Police said the couple would steal money from the restaurants and then hand over the cash for the dealer for hydrocodone or oxycontin.