WHITTIER (CBSLA.com)   —  An investigation into the cause of a deadly accident in a Whittier park is underway.

Saturday, a large eucalyptus tree fell on a wedding party taking pictures. One woman was killed, several other people — including a 4-year-old child– were injured.

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CBS2’s Tina Patel reported from Penn Park Sunday where witnesses to the tragedy still couldn’t shake the horrific images of people being crushed.

“Last night, I couldn’t sleep. I was just thinking about it the whole time honestly,” said witness Leslie Pina.

She was in the park with her family celebrating their grandmother’s birthday yesterday afternoon.

“I  thought it was fireworks or something. but then my brother screamed, he said the tree was falling down,” said Ashley Pina.

“I just saw it fall, people were running. the branches caught them,” said Leslie.

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She said her father helped the groom who appeared to be having trouble breathing.

Other people were trapped under the large branches until firefighters could cut through the tree.

Five people were transported to the hospital. The 4-year-old reportedly suffered head trauma.

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The mother of the bride was reportedly killed.

“I saw people screaming, full of blood. honestly, I didn’t know what to do. I just started crying,” said Leslie.

The park remains closed while an arborist looks at why the tree fell, said city manager Jeff Collier.

He told Patel it wasn’t the first time a large tree came down in the area.

“Not necessarily in our parks, I know that we’ve had a few trees, some of our street trees, we’ve seen an increase, we believe that’s drought related over the last several years, with an increased rate of limb breakage,” said Collier.

He said that city workers are constantly monitoring the health and safety of the trees.

“We have staff out in all of our parks on a daily basis. not necessarily our arborists, but maintenance staff that  are trained to look for any issues with trees,” Collier said.

He says he hasn’t had a chance to reach out to the family involved in Saturday’s tragedy but is saying prayers for them.

“This was a day of celebration that turned to tragedy for them, and our hearts go out to them,” Collier added.

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It is too early to tell if heavy rains and wind Friday night played a role in the tree collapse.