Justice Helen McEntee estimates that more than 80 percent of people applying for asylum in Ireland are coming from Britain
The school, with about 9,700 students, was placed on lockdown after the shooting and all classes were cancelled on Friday.
Authorities have not yet identified the suspect or the victims.
The incident came several hours after an 18-year-old student opened fire with a handgun on the campus of Northern Arizona University in Flagstaff early on Friday, killing one person and wounding three, in the latest in a series of US school shootings.
Texas Southern said there was a separate shooting incident at an apartment complex near campus on Thursday night.