The incident occurred around 3 PM on Sunday, May 1 ... law enforcement authorities tell us they responded to The Mill Works facility located in Westford, MA "for a disturbance," and a report of a man with a firearm.

Once officers arrived on scene, witnesses reported to police that a man who brandished a firearm had fled the scene, according to the Middlesex District Attorney's Office.

Fortunately, witnesses were able to give officers a description of the vehicle the suspect was driving ... and police eventually arrested 34-year-old Jose Mow of Boston, MA in connection with the crimes.

Police say they located the firearm in a diaper bag inside the vehicle Mow was operating.

Mow was hit with 6 charges: Firearm, Carry Without License Ammunition, Possession of Firearm, Store Improperly, Assault with a Dangerous Weapon Public Assembly, Disturbance, and License, Operating After Revocation.

Video footage of the (alleged) horrifying incident was shared on social media ... with kids and parents screaming and running around frantically as they presumably feared for their lives.

We reached out to The Mill Works Sports facility ... and, thankfully, they told us no one was hurt or injured and that all patrons/customers were evacuated to safety in a timely fashion.

"Millworks Sports Facility has emergency protocols in place for mass exodus incidents that are regularly reviewed with employees," they said. "Our number one goal is providing a safe and welcoming environment for all our customers.

"We are pleased that our staff did a tremendous job in assisting our spectators and athletes out of the building during this stressful time for all."

The DA's office says Mow, who was attending a basketball tourney at the facility where his son was playing, allegedly got into an altercation with a parent from the opposing team -- a 48-year-old man from New York.

During the altercation, Mow allegedly brandished the firearm at the other parent ... causing attendees to flee the facility.

“This was a frightening and potentially dangerous situation that has no place in youth sports,” said District Attorney Ryan. “We have put a focus in Middlesex County on building a culture of safe and respectful behavior on the sidelines at these types of events, and that is not what occurred yesterday.

"These types of altercations among adults are unacceptable and can have lasting impacts on our young people.”

Chief of Westford PD Mark Chambers added, “We are very thankful for all the witnesses that came forward to lead to a quick identification of the parties involved, which resulted in the arrest and seizure of the firearm. Additionally, we are extremely fortunate that there were no serious injuries as a result of this incident."

Mow was arraigned this morning in a Massachusetts courtroom earlier today ... where the judge ordered he remains in jail until he posts the $1,000.