Left inset: Sy'mir Draco Vinson (Taylor Funeral Home of Chattanooga). Right inset: Deshundre Vinson (Hamilton County Sheriff's Office). Background: The Tennessee apartment complex pool where cops say Sy'mir Draco Vinson drowned (WTVC/YouTube).

A 4-year-old boy in Tennessee drowned in an apartment complex pool after a 9-year-old he was with was "able to open the pool gate easily" without a key or other access device, a lawsuit says. The child's uncle is charged with murder for allegedly refusing to watch him that day.

"Despite the fact that a young child was able to open the pool gate with minimal effort, no certified lifeguard … or other adult employee was on duty at the pool," a civil complaint filed by the mother of victim Sy'mir Draco Vinson says.

"Tragically, Draco fell into the pool in water that was over his head," the complaint alleges. "Video shows that he struggled as hard as he could for about two minutes, and then he sank under the water."

Draco was at The Reserve at Mountain Pass on Aug. 16 with his 6-year-old brother and three other boys while staying with his uncle, former "America's Got Talent" contestant Deshundre Vinson, who was an "invited guest of a tenant," according to the complaint and police.

Vinson was supposed to be watching them but text messages uncovered by police show a lack of supervision and delayed response after the drowning, local ABC affiliate WTVC reports, citing information obtained from an arrest affidavit. Children younger than 14 were not supposed to use the complex's pool without adult supervision, the affidavit says.

Draco remained underwater for about seven minutes before someone noticed him and pulled him out of the pool.

"It was too late," the complaint states.

Draco was rushed by ambulance to a local hospital, where he spent several days in the intensive care unit before dying on Aug. 20 "as a result of his drowning injuries," according to his mom.

"The pool gate was an unreasonably dangerous condition on defendants' property," the complaint alleges. "The pool gate's closing, latching and/or locking hardware was a dangerous condition that failed to prevent very young children from opening the gate and entering the pool area without a key, other access device, adult assistance, or supervision."

Per the complaint, the pool is located "adjacent to a playground" and within an apartment complex where "numerous young children lived, visited, and played."

Vinson is charged with one count of first degree murder and two counts of aggravated child abuse.

Draco's mother is suing The Reserve at Mountain Pass, LDG The Reserve at Mountain Pass and LDG Development, alleging the apartment complex failed to maintain a safe pool enclosure, failed to provide required supervision, and that the pool was deeper than the posted warning indicated.

"The pool's actual maximum depth exceeded the 3-foot, 6-inch maximum depth represented on defendants' posted sign," the complaint says. "Draco was approximately 3 feet, 8 inches tall. He fell into water that was over his head, struggled for approximately two minutes, and then sank beneath the water."

Draco's mother points to Tennessee and Chattanooga pool-safety requirements concerning barriers, self-closing and self-latching gates, qualified pool operators and certified lifeguards. Her complaint alleges the defendants' failure to provide an effective gate and pool supervision violated those safety requirements and constituted negligence. It also argues that preventing small children from accessing the pool and providing a lifeguard would have been relatively inexpensive compared with the danger involved.

"The cost of providing and maintaining an effective pool-access-control measure capable of preventing small children from entering the pool area unsupervised was slight compared to the foreseeable risk of a child drowning," the complaint states, adding that the same was true of "the cost of providing a lifeguard and/or other adult pool operator."

The complaint alleges those failures directly contributed to Draco's access to the pool, his drowning and his death.

Surveillance footage cited in the arrest affidavit shows Draco walking from the center edge of the pool toward deeper water while holding onto the edge. He appeared to slip and struggle before going underwater.

Vinson became nationally known as part of the R&B group Citi Limitz, which appeared on "America's Got Talent" and "The Ellen DeGeneres Show." His attorney has said the drowning was not intentional and described it as a tragedy for the family, WTVC reports.