Daymond Johnis offering financial aid to the family of the security guard killed in the Buffalo shooting ... reaching out after discovering the guy was a big fan of his.
The son of Aaron Salter Jr., the retired police officer who was working security at the supermarket where the tragic shooting happened, tells TMZ ... Daymond recently called him and struck up a conversation, getting emotional and offering to help with funeral expenses and other bills.
Daymond told Aaron Salter III he saw some photos online of the guy's dad posing with cardboard cutouts of the "Shark Tank" star ... and it turns out watching "Shark Tank" was a family affair in the Salter house.
Aaron, who is being hailed a hero for likely saving the lives of others in the attack, was also an inventor like Daymond ... and his son says DJ told the family his heart goes out to them and he wants to help in any way possible.
When Aaron's son relayed funeral details, Daymond offered to help cover the cost and told the family someone from his camp would be in touch.
We're told Daymond got emotional as the conversation continued ... Aaron's son could hear the pain in Daymond's voice, and towards the end of their talk Daymond offered to help the family with anything they need in the future, urging them not to hesitate.
Aaron's son says his dad was a huge fan of Daymond's and is looking down now, super proud.
Daymond's offer to the family is in addition to a visit from President Biden ... we're told POTUS spoke individually with 9 family members, shaking hands and expressing condolences.
The family is also crowdfunding to set up a non-profit dedicated to Aaron ... with their GoFundMe reaching over $30,000 and counting.