A manhunt for the killer of a married Arkansas couple who were hiking Devil's Den State Park with their two young daughters entered its fourth day on Tuesday, after police released a sketch of a man wanted for questioning and said the killer was likely injured in the attack.Arkansas State Police released the composite sketch Monday night depicting a man wearing a baseball hat. Police called the man a "person of interest" who was seen in the park on Saturday.Clinton Brink, 43, and Cristen Brink, 41, were found dead Saturday afternoon on a walking trail in the park. Their young daughters, ages 9 and 7, were uninjured and are safe with family members, police said.While authorities have not shared details on a possible motive or how the couple was killed, state police released a statement with the sketch, saying the suspect "likely sustained an injury while attacking the couple." No further details were immediately given.COUPLE KILLED AT ARKANSAS' DEVIL'S DEN STATE PARK 'DIED HEROES PROTECTING THEIR LITTLE GIRLS,' FAMILY SAYSThe couples family released a statement on Monday, asking for privacy and for the public to share any information that could help with the investigation with authorities."Clinton and Cristen died heroes, protecting their little girls and they deserve justice," the statement said. "They will forever live on in all of our hearts."The family had just moved from South Dakota to the small city of Prairie Grove in northwest Arkansas, and their water had been connected less than two weeks ago, Mayor David Faulk said. Clinton Brink had been scheduled to start a job as a milk delivery driver Monday in the nearby Fayetteville area, according to Hiland Dairy, his employer.ARKANSAS COUPLE KILLED AT DEVIL'S DEN STATE PARK WHILE HIKING WITH YOUNG DAUGHTERS; SUSPECT AT LARGEPolicedescribed the suspect as a White male with a medium build, who was seen wearing a long-sleeved shirt with the sleeves rolled up, dark pants, a dark ballcap, sunglasses and fingerless gloves. He was also carrying a black backpack, police said.The suspect was also seen driving toward a park exit in a black, four-door sedan possibly a Mazda with tape covering the license plate. The vehicle may have been traveling on State Route 170 or 220, police said.Authorities have urged parkgoers who were at Devils Den on Saturday to check their photos and videos for possible images of the suspect.The bodies of the couple were taken to the state crime lab, which will look to determine the manner and cause of death.Devils Den is located about 140 miles northwest of Little Rock. The remote 2,500-acre park features hiking trails and rock formations.Fox News Digitals Greg Norman, Kyle Schmidbauer and the Associated Press contributed to this report.