Hayden Panettiere's 'Nashville' Costar Charles Esten Shares Story of Their First Meeting

Hayden Panettiere's costar in the hit musical drama "Nashville" Charles Esten shared a loving tribute after her shocking death ... remembering he smacked her with a door during their first meeting.

The actor took to Instagram Monday to share series of photos taken during their time working on the TV show from 2012 to 2018 ... all shots of them flashing huge smiles.

He started off his caption by writing he and his wife -- Patty Hanson -- were shocked to learn of Hayden's death ... before he launched into the story of how they met.

Charles explains he finished his audition for the show -- acting out some scenes and belting out a couple tunes. When he opened the door to leave, he says he smacked someone with it pretty dang hard ... and that someone was Hayden.

According to Charles, Hayden had been listening at the door ... but instead being embarassed or mad about the door slam, he says she just smiled and told him he'd crushed the audition.

He says he jokingly told her he'd see her on set when they parted ways that day even though neither had landed their roles yet ... but, it just happened to work out.

Charles writes Hayden was "extraordinarily talented, infusing her larger-than-life character with all the heart, charisma, humor, whip-smart intelligence, and flat-out magic that were, alongside whatever troubles and pain she carried, a part of her own personal palette. What a great gift it was to act with her, sing with her, and to just be her friend."

As we reported ... Hayden died in Greenville, South Carolina on Sunday. First responders were called to a residence at 1:51 PM but were unable to revive her.

Narcan -- medicine meant to reverse the effects of a drug overdose -- was found in the apartment ... and dispatch audio also indicates she may have OD'd -- although the cause and manner of her death are not yet known.

Charles is far from the only celeb to give Hayden her flowers after passing ... stars like Emma Roberts, Viola Davis, 50 Cent and Tim Allen have all shared posts in her honor.

She was 36.