SCHNECKSVILLE, Pa. >> A young giraffe recently brought to a Pennsylvania zoo has died after injuring his neck during unexplained aggressive behavior, zoo officials said.

Six-year-old Ernie, a Masai giraffe, was brought to Lehigh Valley Zoo from the Kansas City Zoo in Missouri last week along with his 16-year-old father, Murphy, as part of a $3.8 million expansion of the Schnecksville zoo’s African animals exhibit.

Ernie arrived Friday after an 18-hour road trip in a special trailer, officials said in a written account Sunday. Murphy arrived days earlier. Zoo officials say Murphy showed affection to the young giraffe, nuzzling his face, but Ernie later became aggressive for unknown reasons and the animals were separated.

Saturday night, Ernie again became aggressive and critically injured his neck in a stall, officials said. The zoo veterinarian reached out to giraffe specialists, but Ernie died Sunday afternoon, they said.

“We are having the most difficult time finding the words to convey how heartbroken we are, and we hope you will join us as we mourn the loss of Ernie,” zoo president and CEO Melissa Borland said in a statement Sunday.

The Association of Zoos and Aquariums will be involved in an investigation into the animal’s death.

“You do hear about giraffe accidents that occur. They are rare, but it doesn’t make them any less tragic. Everyone was surprised by this one,” association spokesman Rob Vernon told The (Allentown) Morning Call.

In March, North Carolina Zoo officials said a 9-year-old female reticulated giraffe, named Jamili, was found unresponsive after becoming entangled in a device meant to keep the animals intellectually stimulated and engaged.

The 29-acre Lehigh Valley Zoo is inside the Trexler Nature Preserve. Besides giraffes, the African exhibit will include a lion, hyrax, wildebeest and tortoise. It will have elevated feeding stations for the giraffes. Zoo officials haven’t said whether the planned opening of the giraffe exhibit in the second week of June will be delayed.