Authorities in Pontiac, Michigan, likely stopped a mass shooting at a high school graduation ceremony earlier this week, sheriff says

Michigan authorities found two handguns with 40 -round magazines at a high school graduation.

Deputies arrested a 19-year-old suspect, but are still looking for a person of interest in the alleged mass shooting plot.

Michigan Gov. Gretchen Whitmer said she is grateful for first responders for "acting fast and saving lives in Pontiac ".