The 20-year-old Spring Lake man suffered serious cuts to his neck, right hand and left leg below the knee, police said.
He had multiple cuts over his body, said Sgt. Clint Holt of the Grand Haven Department of Public Safety.
An ambulance transported the man to North Ottawa Community Hospital after the 12:54 p.m. incident.
Jim Stuberg of the CPA firm Draper Bialik & Co., said the man had just made a delivery and left their office when they heard his cries for help.
“All we heard was breaking of glass and the guy hollering for someone to call 911,” Stuberg said.
He and some of his co-workers grabbed towels to help stop the bleeding until emergency personnel arrived.
Police said the man was looking down at a receipt when he went through the sidelight adjacent to the front door.
The man's name was not available at this time.