Windsor police are investigating two separate weapons calls.
The first was at a home at Mercer Street and Elliott Street just before 2 p.m. on Wednesday and the second was at a home on Arthur Road near Ypres Street an hour later.
The two incidents are related but police have not elaborated.
Several times during the standoff on Arthur Road that lasted six hours, Emergency Services Unit officers called for a woman to come out because they were not leaving. They tried negotiating with her saying they were investigating shots fired, but to no avail. At one point officers entered the house with guns drawn but came up empty. Police finally cleared the house at around 8:30 p.m.
One young man and three young women were either arrested or surrendered.
Some neighbours, who wish to remain anonymous, called the home "a drug house" and said there had been police activity at the house every couple of weeks for a few months. One neighbour said the house was raided just a couple of weeks ago.
Further information about the incident is expected to be released on Thursday.