LOMBARD, Ill. (CBS) — An Islamic school in west suburban Lombard is at least the second Muslim institution to report an attack this past weekend.

The Council of Islamic Organizations of Greater Chicago says the College Preparatory School of America, an Islamic school at 331 W. Madison St. in Lombard, was subjected to vandalism on Sunday night.

The council says someone hurled a 7-Up bottle filled with acid and other unspecified materials at the school during the nighttime Ramadan prayers.

During the prayer session, worshipers heard a loud bang and went to find an empty bottle thrown on the window of the school. No one was injured.

No one was in custody as of just before noon Monday, and there were on suspects, Lombard police told CBS 2.

The latest incident comes just two nights after air rifle shots were fired at a mosque in north suburban Morton Grove.

Authorities began investigating after a Friday night shooting, while worshipers were celebrating the holy month of Ramadan at the Muslim Education Center, 8601 N. Menard Avenue, about 9 p.m., according to police and mosque officials.

Off-duty Chicago Police officers, who have been hired to provide additional security at the mosque during Ramadan activities, called Morton Grove police after they saw an object whiz by and hit the building just above the head of one of the officers, according to Kamran Hussain, Vice President of the Muslim Community Center of Chicago, which owns the mosque.

No one was injured in that incident.

The man suspected of firing the shots – David Conrad, 51, who lives just east of the house of worship – was charged with three counts of aggravated discharge of a firearm, a class X felony, and one count of criminal damage to property, a class 4 felony.

Police in Morton Grove said prosecutors rejected hate crime charges.

The man’s home abuts the mosque parking lot, which has been cause for a number of disputes between the building’s owners and the neighbor, Hussain said. He has lived there for about 12 years.