COLORADO SPRINGS, COLO. -- Colorado Springs Police officers have arrested a man believed to be responsible for seven pharmacy robberies since Oct. 13.

Officers arrested 22-year-old Nathan Gasser at the Windmill Apartments around 12:25 p.m. Friday after gathering information following Wednesday's Safeway robbery in Fountain.

In all seven cases, a suspect matching Gasser's description entered a pharmacy or drug store, threatened the clerk with a gun or mentioned he had one, and demanded hydromorphone.

Officers said Gasser tried disguising himself with a wig or scarf in several of the robberies.

Gasser is believed to have robbed the following places:

- Safeway in the 1400 block of South Murray Boulevard (Oct. 13)
- Walgreens in the 1900 block of South Chelton Road (Oct. 27)
- Walgreens in the 1800 block of Southgate Road (Nov. 2)
- Walgreens in the 300 block of South Circle Drive (Nov. 22)
- Safeway in the 2800 block of North Powers Boulevard (Nov. 25)
- Safeway in the 6500 block of South Academy Boulevard (Dec. 2)
- Walgreens in the 1800 block of Southgate Road (Dec. 3)

Gasser is also a "probable" suspect in at least eight other pharmacy robberies, including Wednesday's Safeway robbery and robberies in Arapahoe, Littleton and Parker countries.

The investigation is ongoing.