Chief Steve Drew stated the incident occurred at Richneck Elementary School in the city of Newport News shortly after 14:00 local time (19:00 GMT).
Mr Drew has stated that this was not “an accidental shooting,” albeit it is unknown how the toddler obtained the firearm.
The educator, who has not been identified but is thought to be in her 30s, suffered severe injuries that may prove fatal.
Doctors at the local hospital closely monitored her after she was brought there. After an argument, the incident unfolded in a first-grade classroom (for children aged six and seven).
Mr Drew, however, highlighted that this shooting was an isolated event and that police “did not have a situation where someone was going around the school shooting.”
Officials stated that not all of the school’s 550 kids were inspected during random metal detector checks, despite the school’s use of metal detectors.
Police stated the youngster had used a firearm but wouldn’t specify which one.
Dr George Parker, the superintendent of the affected schools, has promised an investigation into “any instance that may have occurred that may have caused this incident.”
“This is terrible, something like this should never occur,” Dr Parker added. “We want to ensure nothing like this happens again.”
A Monday closure was announced, and he assured everyone involved that counselling and other resources would be made available to help students and parents cope with the tragedy.
The incident was described as “a dark day for Newport News” by Mayor Phillip Jones, who had been in office for only three days.
He assured reporters that the team would recover from their setback and emerge even more powerful.
According to Virginia Governor Glenn Youngkin, his administration is “ready to help in any manner we can” and has supported local leaders.
I’m keeping an eye on things and hoping for everyone’s safety, he tweeted.
About 70 miles (112 km) to the south of the state capital Richmond is the city of Newport News, home to approximately 180,000 people.