A Braintree man is facing aggravated assault charges after police say he put something in a co-worker’s drink.

The incident happened July 25 at the Gifford Medical Center in Randolph.

Authorities say the employee went to the emergency room after suspecting their drink was tainted.

An investigation led to the arrest of another worker at the hospital, 63-year-old Wayne Parezo.

Police say the investigation is ongoing.