There are two elements that make this passage read like an eyewitness account. Firstly, the use of the present tense for the verbs in Mark 7:32. A literal translation of verse 32 would be, And they bring to him a deaf man who spoke with difficulty and they beg him that he may lay on him the hand.
The second element is the use of the Hebrew or Aramaic word “Ephphatha” (see Mark 7:34). As Peter was an important source of information for Mark, this probably derives from Peter’s witness of the healing.1
31 Then he returned from the region of Tyre and went through Sidon to the Sea of Galilee, in the region of the Decapolis.