AMHERST — A guest at a house party on Main Street is facing assault and battery charges after allegedly urinating on a woman delivering a pizza early Sunday morning, according to police.

The 20-year-old Stoughton man was on the roof of the home at 675 Main St. at 1:24 a.m. when the delivery driver arrived, and then committed the alleged assault, Detective Nicholas Chandler said.

Police also warned a tenant at the home that he is responsible for the actions of a guest and could be issued tickets or be subject to arrest under the town’s nuisance house bylaw.

The assault was the most serious incident during a weekend in which police handled just 279 calls for service, lower than in recent fall weekends. Chandler said cold and wet weather during part of Saturday contributed to the reduced amount of service calls.

In fact, just one loud party led to arrests for violating the town’s noise bylaw. That occurred Sunday at 12:27 a.m. at 16 Sunrise Ave., when responding officers only got limited cooperation from the four tenants.

On Friday at 11:11 p.m., police responded to Summer Street where a party registered through the Party Smart program at the University of Massachusetts was cleared out, but people continued to loiter in the road. Officers assisted them in getting on their way. Similarly at 12:54 a.m. Sunday on Northampton Road, police dispersed pedestrians who were clogging up the road.

Police were called to Alpha Tau Gamma, 118 Sunset Ave., at 12:10 a.m. Sunday for people causing trouble and trying to instigate fights, Chandler said. Three men were located, including one with a serious laceration on his face that required him to be treated by the Amherst Fire Department paramedics.

Unlike during last weekend when an intruder got into a home, residents called police twice over the weekend out of concern that something similar might happen.

At 37 Meadow St. at 12:11 a.m. Sunday, someone was reported trying to break in through a basement window.

“It certainly alarmed the residents there,” Chandler said.

K-9 Marvin was on the scene with an officer who located the suspect. The college-age man said he was trying to find a friend’s party and had no intention of entering the home.

Then, at 12:32 a.m, a resident at 152 Gray St. reported people banged and scratched on her windows for the second straight night. Officers found a college-age man covered in mud who admitted to being in the back yard, but thought he was at his friend’s house.

Only two people are being summoned to court for liquor law violations, while 13 people were warned for being minors in possession of alcohol or carrying opening containers on public ways.

Scott Merzbach can be reached at smerzbach@gazettenet.com.