When State Trooper Nate Monteiro pulled up behind Alexandra Schirmer on Wednesday afternoon in the breakdown lane on Route 24 in Raynham, she thought she was in trouble. Instead, she’d found a guardian angel. Schirmer, a certified nursing assistant in Bridgewater, was heading home from work with her 4-month-old son, Sebastian, and they were stuck in heavy traffic. “It was so hot and Sebastian wouldn’t stop crying to the point he was making himself choke. He was just hungry. I couldn’t take it anymore,” the Berkley native posted on Facebook. Schirmer, 22, pulled over into the breakdown lane to give Sebastian a bottle. When Monteiro pulled up behind her, she was so scared, she waved the baby bottle out the window, she said. But she had nothing to worry about. “He was so nice,” Schirmer said Thursday. Monteiro went back to his cruiser and came back, not with a ticket, but with a Beanie Baby for Sebastian. Then Monteiro sat in his cruiser and waited there until Schirmer was done feeding Sebastian to make sure they were safe, she said. “It was pretty cool,” Schirmer posted.